April 16, 2017

Australia at Night

This shows the night lights of Australia as observed by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite in April and October 2012. The composite image includes manmade light sources and the light of wildfires. The data were acquired over nine days in April 2012 and thirteen days in October 2012, and it took the satellite 312 orbits and 2.5 terabytes of data to get a clear shot of every parcel of Earth’s land surface.

The extent of the lighting in the Outback and bush country is a function of composite imaging. Fires and other lights that were detected on one day were integrated into the composite, multi-day picture despite being temporary phenomena. Because different lands burned at different times that the satellite passed over, the cumulative result is the appearance of a massive blaze. But while the cities are fixed, the fires were temporary, moveable features. The night lights data set is a scientific work in progress, and the maps will be refined and improved over time.

Not every light in the night view matches up with a fire—partly because the fire map does not include fires from April and partly because not every fire leaves a scar that is detectable from space. Even simple cloud cover could prevent burn scars from being observed.

Aside from the fires, some of the night lights appearing in uninhabited areas can be attributed to natural gas flares, lightning, oil drilling or mining operations, and fishing boats—all of which can show up as points of light. One example is natural gas drilling in the Bakken Formation in North Dakota; another is the fishing boats plying the seas of Asia.

And ultimately, the new images of Earth at night are ripe for new discoveries. It’s easy to say that lands are uninhabited or barren—that there’s nothing out there to make light. But the satellite says there is light, so we should probably go take a look at what we have been overlooking or simply could not see before.